Since 1972, the increases of the real cost of oil has prompted the evaluation of alternative technologies for the production of liquid fuels. Of particular interest is the use of biomass derived alcohol as a gasoline substitute or supplement. In view of this increased interest, the present invention provides a nutrient composition that is suitable for increasing the fermentation rate by yeast to provide alcohol.
Glucose is converted to ethanol by yeast fermentation according to the following equation: EQU C.sub.6 H.sub.12 O.sub.6 .fwdarw.2C.sub.2 H.sub.5 OH+2CO.sub.2
Additionally, quantities of glycerol and higher alcohols are also produced, the amount being dependent on the strain of yeast and fermentation conditions. Such reactions are catalyzed by enzymes.
Nitrogen and phosphorus are two of the essential elements for the growth of yeast. It is often necessary to supplement nitrogen and phosphorus sources, and occasionally other nutrients and micronutrient, to increase the acohol fermentation rate. Typically, supplemental phosphorus is provided as the orthophosphate.
U.S. Pat. No. 4,727,031, disclosed studies of aerobic systems using bacteria, that indicated, generally, the growth rate of bacteria decreased as the phosphate chain length increased. A synergistic combination of orthophosphate and a short chain condensed phosphate such as pyrophosphate or tripolyphosphate in a nutrient system was used to stimulate growth of aerobic bacteria. The nutrient system was such that 5% to 65% by weight of the total phosphate combination was the pyrophosphate and/or tripolyphosphate.
International Patent Publication No. WO 83/02952 disclosed the use of the inorganic pyrophosphate ions to stimulate the growth of some anaerobic or aerobic bacteria. The pyrophosphate ion oxidizes adenosine diphosphate (ADP) to adenosine tripolyphoshate (ATP) in anaerobic bacteria. ATP is known to be the primary carrier of chemical energy in biological processes, and therefore, stimulates the growth of the bacteria.
The above publications fail to disclose the use of polyphosphate, such as tripolyphosphate and Kurrol's salt, in combination with orthophosphate salts, or certain nutrients in combination with phosphate polymers to increase the fermentation rates of yeasts.